Living dangerously: how Helicobacter pylori survives in the human stomach

Molecular detection of Helicobacter pylori based on the presence of cagA and vacA virulence genes in dental plaque from patients with periodontitis

Background/purpose

Helicobacter pylori (H. pylori) infection is the most common in the world and is associated with various gastrointestinal pathologies, including chronic gastritis, peptic ulcers, and gastric cancer. The prevalence is associated with socioeconomic conditions, with this infection being more common in developing countries than in developed countries. The presence and permanence of H. pylori in the oral cavity has been reported, but its role is controversial. The aim of this study was to determine the prevalence of H. pylori in dental plaque of patients with periodontitis.

Materials and methods

A cross-sectional study was carried out and Periodontal Screening and Recording (PSR) index was determined. 38 dental plaque samples were taken and total DNA was extracted and qPCR was performed.

Results

60.5% of the samples (n = 23) were positive for the presence of H. pylori by the amplification of the 16S rRNA and vacA genes. In addition, cagA gene was detected in 21.7% (n = 5) of H. pylori-positive. A significant relationship between periodontal status and H. pylori oral infection was found (P ≤ 0.05); patients with initial and moderate periodontitis were the most affected with 39.1% and 30.4%, respectively.

Conclusion

Our results suggest that the prevalence of H. pylori in the oral cavity could be related to the progression of periodontal disease. Therefore, oral hygiene and treatment for the elimination of oral H. pylori could stop the progression of periodontal disease.

Intracellular Degradation of Helicobacter pylori VacA Toxin as a Determinant of Gastric Epithelial Cell Viability

Helicobacter pylori VacA is a secreted pore-forming toxin that induces cell vacuolation in vitro and contributes to the pathogenesis of gastric cancer and peptic ulcer disease. We observed that purified VacA has relatively little effect on the viability of AGS gastric epithelial cells, but the presence of exogenous weak bases such as ammonium chloride (NH₄Cl) enhances the susceptibility of these cells to VacA-induced vacuolation and cell death. Therefore, we tested the hypothesis that NH₄Cl augments VacA toxicity by altering the intracellular trafficking of VacA or inhibiting intracellular VacA degradation. We observed VacA colocalization with LAMP1- and LC3-positive vesicles in both the presence and absence of NH₄Cl, indicating that NH₄Cl does not alter VacA trafficking to lysosomes or autophagosomes. Conversely, we found that supplemental NH₄Cl significantly increases the intracellular stability of VacA. By conducting experiments using chemical inhibitors, stable ATG5 knockdown cell lines, and ATG16L1 knockout cells (generated using CRISPR/Cas9), we show that VacA degradation is independent of autophagy and proteasome activity but dependent on lysosomal acidification. We conclude that weak bases like ammonia, potentially generated during H. pylori infection by urease and other enzymes, enhance VacA toxicity by inhibiting toxin degradation.

Protein changes in gastric epithelial cells RGM-1 in response to Helicobacter pylori infection

Helicobacter pylori-induced inflammation significantly increases the risk of gastric cancer. To investigate the role of H. pylori infection in gastric epithelial cell carcinogenesis, flow cytometry was used to analyze the apoptosis of gastric epithelial cells infected by H. pylori. Next, LTQ MS mass spectrometry (MS) was applied to identify protein changes in gastric epithelial cells infected with H. pylori, and then bioinformatics was adopted to analyze the cellular localization and biological function of differential proteins. LTQ MS/MS successfully identified identified 22 differential proteins successfully, including 20 host-cell proteins and two H. pylori bacterial proteins. Also, human proteins were located in all areas of cells and involved in various cell biological functions. The oncogene proteins p53, p16, and C-erbB-2 proteins in H. pylori-infected RGM-1 cells were remarkably increased from the analysis by Western blot analysis. H. pylori infection of gastric epithelial cells leads to changes in various protein components in the cell, and enhances the expression of oncogene proteins, thereby increasing the possibility of possibility of carcinogenesis of H. pylori infection.

The lipoprotein HP1454 of Helicobacter pylori regulates T-cell response by shaping T-cell receptor signalling

Helicobacter pylori (HP) is a Gram-negative bacterium that chronically infects the stomach of more than 50% of human population and represents a major cause of gastric cancer, gastric lymphoma, gastric autoimmunity, and peptic ulcer. It still remains to be elucidated, which HP virulence factors are important in the development of gastric disorders. Here, we analysed the role of the HP protein HP1454 in the host-pathogen interaction. We found that a significant proportion of T cells isolated from HP patients with chronic gastritis and gastric adenocarcinoma proliferated in response to HP1454. Moreover, we demonstrated in vivo that HP1454 protein drives Th1/Th17 inflammatory responses. We further analysed the in vitro response of human T cells exposed either to an HP wild-type strain or to a strain with a deletion of the hp1454 gene, and we revealed that HP1454 triggers the T-cell antigen receptor-dependent signalling and lymphocyte proliferation, as well as the CXCL12-dependent cell adhesion and migration. Our study findings prove that HP1454 is a crucial bacterial factor that exerts its proinflammatory activity by directly modulating the T-cell response. The relevance of these results can be appreciated by considering that compelling evidence suggest that chronic gastric inflammation, a condition that paves the way to HP-associated diseases, is dependent on T cells.

Association of alcohol consumption with the risk of stomach cancer in a Japanese population: a prospective cohort study

Biological studies have provided confirmation of alcohol-related carcinogenesis in the stomach, but the association between alcohol consumption and the risk of stomach cancer remains controversial. We aimed to investigate whether quantitative alcohol intake is associated with the risk of stomach cancer in a large prospective cohort study among a Japanese population. Study participants included 30 714 participants (14 171 men and 16 543 women) aged 35 years or older, who were enrolled in the Takayama study launched on 1 September 1992. Alcohol consumption was assessed quantitatively using a validated food frequency questionnaire. According to alcohol intake (g/day), male participants were classified into quartile groups: Q1, Q2, Q3, or Q4. Female participants were classified into three groups: nondrinkers, and drinkers below or above the median alcohol level. We estimated the hazard ratios and 95% confidence intervals (CIs) for stomach cancer adjusted for age, smoking, BMI, education, total energy intake, salt intake, physical activity, and medical history of diabetes mellitus for each alcohol intake group using the Cox proportional hazards regression model. By the end of March 2008, a total of 678 participants had been diagnosed with stomach cancer. For men, the multivariate-adjusted HRs of stomach cancer for Q2, Q3, and Q4 relative to Q1 were 1.39 (95% CI: 1.07-1.81), 1.35 (95% CI: 1.02-1.79), and 1.38 (95% CI: 1.02-1.87), respectively. In women, no associations were observed. These data suggest that alcohol consumption could be associated with an increased risk of stomach cancer among Japanese men.

Synthesis of some novel quinazolin-4(3H)-one hybrid molecules as potent urease inhibitors

A new series of quinazolinone hybrid molecules containing coumarin, furan, 1,2,4-triazole and 1,2,4-thiadiazole rings was designed, synthesized, and screened for their urease inhibition activities. All newly synthesized compounds showed outstanding urease inhibitory potentials with IC₅₀ values ranging between 1.26 ± 0.07 and 7.35 ± 0.31 μg/mL. Among the series, coumarin derivatives (10a-d) exhibited the best inhibitory effect against urease in the range of IC₅₀  = 1.26 ± 0.07 to 1.82 ± 0.10 μg/mL, when compared to standard urease inhibitors such as acetohydroxamic acid and thiourea (IC₅₀  = 21.05 ± 0.96 and 15.08 ± 0.71 μg/mL, respectively). Molecular docking studies were also performed to analyze the binding mode of compound 10b, and supported the experimental results.

Mouse Models Of Helicobacter Infection And Gastric Pathologies

Helicobacter pylori is a gastric pathogen that is present in half of the global population and is a significant cause of morbidity and mortality in humans. Several mouse models of gastric Helicobacter infection have been developed to study the molecular and cellular mechanisms whereby H. pylori bacteria colonize the stomach of human hosts and cause disease. Herein, we describe protocols to: 1) prepare bacterial suspensions for the in vivo infection of mice via intragastric gavage; 2) determine bacterial colonization levels in mouse gastric tissues, by polymerase chain reaction (PCR) and viable counting; and 3) assess pathological changes, by histology. To establish Helicobacter infection in mice, specific pathogen-free (SPF) animals are first inoculated with suspensions (containing ≥10⁵ colony-forming units, CFUs) of mouse-colonizing strains of either Helicobacter pylori or other gastric Helicobacter spp. from animals, such as Helicobacter felis. At the appropriate time-points post-infection, stomachs are excised and dissected sagittally into two equal tissue fragments, each comprising the antrum and body regions. One of these fragments is then used for either viable counting or DNA extraction, while the other is subjected to histological processing. Bacterial colonization and histopathological changes in the stomach may be assessed routinely in gastric tissue sections stained with Warthin-Starry, Giemsa or Haematoxylin and Eosin (H&E) stains, as appropriate. Additional immunological analyses may also be undertaken by immunohistochemistry or immunofluorescence on mouse gastric tissue sections. The protocols described below are specifically designed to enable the assessment in mice of gastric pathologies resembling those in human-related H. pylori diseases, including inflammation, gland atrophy and lymphoid follicle formation. The inoculum preparation and intragastric gavage protocols may also be adapted to study the pathogenesis of other enteric human pathogens that colonize mice, such as Salmonella Typhimurium or Citrobacter rodentium.

Multi-omics and temporal dynamics profiling reveal disruption of central metabolism in Helicobacter pylori on bismuth treatment

Integration of multi-omics enables uncovering cellular responses to stimuli or the mechanism of action of a drug at a system level. Bismuth drugs have long been used for the treatment of Helicobacter pylori infection and their antimicrobial activity was attributed to dysfunction of multiple proteins based on previous proteome-wide studies. Herein, we investigated the response of H. pylori to a bismuth drug at transcriptome and metabolome levels. Our multi-omics data together with bioassays comprehensively reveal the impact of bismuth on a diverse array of intracellular pathways, in particular, disruption of central carbon metabolism is systematically evaluated as a primary bismuth-targeting system in H. pylori. Through temporal dynamics profiling, we demonstrate that bismuth initially perturbs the TCA cycle and then urease activity, followed by the induction of oxidative stress and inhibition of energy production, and in the meantime, induces extensive down-regulation in H. pylori metabolome. The present study thus expands our knowledge on the inhibitory actions of bismuth and provides a novel systematic perspective of H. pylori in response to a clinical drug that sheds light on enhanced therapeutic methodologies.

Inflammasome activation and regulation during Helicobacter pylori pathogenesis

Helicobacter pylori is a leading cause of gastric cancer worldwide, its type four secretary toxin CagA is cited to be primarily responsible for it. Other virulence factors such as urease, VacA, HopQ, BabA and SabA are responsible for bacterial survival in acidic environment, adherence and cellular damage but its molecular mechanism is not completely understood. A number of pathogens including bacteria, fungi and virus are involved in the regulation of cellular machinery of inflammasome. Inflammasomes are multimeric protein complexes formed after external stimuli such as PAMPs/DAMPs or salt crystals and activates cellular caspases causes inflammation via pro-inflammatory cytokines. Virulence factors associated with microbial pathogens causes' cellular damage through damaging mitochondria, rupturing lysosome, producing endoplasmic stress and dysregulation of cellular ions balance. These cellular dysfunctioning leads to oxidative stress, cathepsin B production, nuclear and mitochondrial DNA damage which activates inflammasome machinery, pro-inflammatory cytokine release and cellular death known as pyroptosis. The mechanism of inflammasome induction by H. pylori is not studied extensively and very few virulence factors such as UreB, CagA, FlaA and VacA and their role in inflammasomes is established. This review elaborates the mechanism of inflammasomes regulation and elucidates the pathways through which H. pylori regulates inflammasome activation.

Cellular stress and redox activity proteins are involved in gastric carcinogenesis associated with Helicobacter pylori infection expressing high levels of thioredoxin-1

Helicobacter pylori infection is related to the development of gastric diseases. Our previous studies showed that high thioredoxin-1 (Trx1) expression in H. pylori can promote gastric carcinogenesis. To explore the underlying molecular mechanisms, we performed an isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomic analysis of stomach tissues from Mongolian gerbil infected with H. pylori expressing high and low Trx1. Differences in the profiles of the expressed proteins were analyzed by bioinformatics and verified using Western blot analysis. We found three candidate proteins, 14-3-3α/β, glutathione-S-transferase (GST), and heat shock protein 70 (HSP70), in high Trx1 tissues compared with low Trx1 tissues and concluded that cellular stress and redox activity-related proteins were involved in the pathogenesis of gastric cancer associated with H. pylori Trx1.

Widespread Antibiotic, Biocide, and Metal Resistance in Microbial Communities Inhabiting a Municipal Waste Environment and Anthropogenically Impacted River

Landfill leachate is a persistent contamination threat for terrestrial waters. Microbial metabolism in landfills transforms contaminants and contributes to greenhouse gas emissions. A better understanding of landfill-associated microbial communities will inform bioremediation of solid waste environments and improve pathogen monitoring. We leveraged shotgun metagenomics to investigate the microbial communities of the Riverton City dump and the adjoining Duhaney River near Kingston City, Jamaica. We identified no overlap between the microbial communities inhabiting the Riverton City dump leachate and the Duhaney River. Both communities are predicted to degrade aromatic compounds, which are ubiquitous environmental pollutants. Adversely, microbes in both environments are predicted to withstand widely used antibiotics, antiseptics, and metal contamination. The absence of evidence for microbial transfer from the leachate to the river is encouraging; however, the Duhaney River contained several organisms with predicted pathogenic lifestyles, indicating that the river represents a human health risk regardless of impact from the dump.

The Riverton City dump is Jamaica’s largest solid waste disposal site, but it lacks engineered protection for leachate containment and treatment. Shotgun metagenomics was used to survey the microbial communities in the Riverton City dump leachate and in surface waters of the Duhaney River, an urban waterway abutting the dump. The community within the leachate pond was taxonomically distinct from that found in the surface waters of the Duhaney River. Higher microbial diversity was observed within the dump leachate, with members of the Bacteroidetes, Firmicutes, Gammaproteobacteria, Deltaproteobacteria, and Tenericutes being the most abundant, while the river community was dominated by Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria. The microbial communities exhibit similar functional potential profiles, including chemoorganoheterotrophy as the dominant metabolism, and the potential to degrade aromatic compounds. From reconstruction of metagenome-assembled genomes (MAGs), organisms within both environments are predicted to survive in the presence of multiple antibiotics, antiseptics, biocides, and metals. Strong virulence potential coincided with the most diverse multiple resistance profiles in 1 of 5 leachate MAGs and 5 of 33 river MAGs. Unexpectedly, the microbial resistance profiles were more varied and widespread in the river populations, where we had expected the chemical composition of the leachate to select and enrich for resistance characteristics. This study provides valuable insights into the total functional potential of a landfill leachate microbial community and identifies possible human health hazards within the Duhaney River and Riverton City dump, urban environments with the potential to impact human populations.

IMPORTANCE Landfill leachate is a persistent contamination threat for terrestrial waters. Microbial metabolism in landfills transforms contaminants and contributes to greenhouse gas emissions. A better understanding of landfill-associated microbial communities will inform bioremediation of solid waste environments and improve pathogen monitoring. We leveraged shotgun metagenomics to investigate the microbial communities of the Riverton City dump and the adjoining Duhaney River near Kingston City, Jamaica. We identified no overlap between the microbial communities inhabiting the Riverton City dump leachate and the Duhaney River. Both communities are predicted to degrade aromatic compounds, which are ubiquitous environmental pollutants. Adversely, microbes in both environments are predicted to withstand widely used antibiotics, antiseptics, and metal contamination. The absence of evidence for microbial transfer from the leachate to the river is encouraging; however, the Duhaney River contained several organisms with predicted pathogenic lifestyles, indicating that the river represents a human health risk regardless of impact from the dump.

Molecular Mechanisms of H. pylori-Induced DNA Double-Strand Breaks

Infections contribute to carcinogenesis through inflammation-related mechanisms. H. pylori infection is a significant risk factor for gastric carcinogenesis. However, the molecular mechanism by which H. pylori infection contributes to carcinogenesis has not been fully elucidated. H. pylori-associated chronic inflammation is linked to genomic instability via reactive oxygen and nitrogen species (RONS). In this article, we summarize the current knowledge of H. pylori-induced double strand breaks (DSBs). Furthermore, we provide mechanistic insight into how processing of oxidative DNA damage via base excision repair (BER) leads to DSBs. We review recent studies on how H. pylori infection triggers NF-κB/inducible NO synthase (iNOS) versus NF-κB/nucleotide excision repair (NER) axis-mediated DSBs to drive genomic instability. This review discusses current research findings that are related to mechanisms of DSBs and repair during H. pylori infection.

Influence of the viscosity of healthy and diseased human mucins on the motility of Helicobacter pylori

We present particle tracking microrheology results on human mucins, isolated from normal surface and gland mucosa and one tumor sample, and examine the motility of Helicobacter pylori in these mucins. At 1.5% concentration human mucin solutions are purely viscous, with viscosity η (gland mucin) > η (surface mucin) > η (tumor mucin). In the presence of motile H. pylori bacteria, particle diffusion is enhanced, with diffusivity D_+bac(tumor mucin) > D_+bac(gland mucin) > D_+bac(surface mucin). The surface and tumor mucin solutions exhibit an elastic response in the presence of bacteria. Taken together these results imply that particle diffusion and active swimming are coupled and impact the rheology of mucin solutions. Both J99 wild type (WT) and its isogenic ΔbabA/ΔsabA mutant swam well in broth or PGM solutions. However, the human mucins affected their motility differently, rendering them immotile in certain instances. The distribution of swimming speeds in human mucin solutions was broader with a large fraction of fast swimmers compared to PGM and broth. The bacteria swam fastest in the tumor mucin solution correlating with it having the lowest viscosity of all mucin solutions. Overall, these results suggest that mucins from different tissue locations and disease status differ in their microrheological properties and their effect on H. pylori motility.

In Vitro Inhibition of Helicobacter pylori Growth by Redox Cycling Phenylaminojuglones

Infection by Helicobacter pylori increases 10 times the risk of developing gastric cancer. Juglone, a natural occurring 1,4-naphthoquinone, prevents H. pylori growth by interfering with some of its critical metabolic pathways. Here, we report the design, synthesis, and in vitro evaluation of a series of juglone derivatives, namely, 2/3-phenylaminojuglones, as potential H. pylori growth inhibitors. Results show that 5 out of 12 phenylaminojuglones (at 1.5 μg/mL) were 1.5-2.2-fold more active than juglone. Interestingly, most of the phenylaminojuglones (10 out of 12) were 1.1-2.8 fold more active than metronidazole, a known H. pylori growth inhibitor. The most active compound, namely, 2-((3,4,5-trimethoxyphenyl)amino)-5-hydroxynaphthalene-1,4-dione 7, showed significant higher halo of growth inhibitions (HGI = 32.25 mm) to that of juglone and metronidazole (HGI = 14.50 and 11.67 mm). Structural activity relationships of the series suggest that the nature and location of the nitrogen substituents in the juglone scaffold, likely due in part to their redox potential, may influence the antibacterial activity of the series.

Anti-Helicobacterpylori effectiveness and targeted delivery performance of amoxicillin-UCCs-2/TPP nanoparticles based on ureido-modified chitosan derivative

The amoxicillin-UCCs-2/TPP nanoparticles constructed with ureido-modified chitosan derivative UCCs-2 and sodium tripolyphosphate (TPP) played an important role to deliver drug to achieve more efficacious and specific eradication of Helicobacterpylori (H. pylori) in vitro. In this study, the anti-H. pylori effectiveness in vivo and uptake mechanism was investigated in details, including the effect of temperature, pH values and the addition of competitive substrate urea on uptake. Compared with unmodified nanoparticles, a more efficacious and specific anti-H. pylori activities were obtained in vivo by using this biological chitosan derivative UCCs-2. Histological staining and immunological analysis verified that the amoxicillin-UCCs-2/TPP nanoparticles could diminish the proinflammatory cytokines levels and alleviate the inflammatory damages caused by H. pylori infection. The uredio-modified nanoparticles also have favorable gastric retention property, which is beneficial for the oral drug delivery to targeted eradicate H. pylori infection in stomach. These findings suggest that this targeted drug delivery system may serve for specific treatment of H. pylori infection both in vitro and in vivo, which can also be used as promising nanocarriers for other therapeutic reagents to target H. pylori.

Modulation of Intestinal Paracellular Transport by Bacterial Pathogens

The passive and regulated movement of ions, solutes, and water via spaces between cells of the epithelial monolayer plays a critical role in the normal intestinal functioning. This paracellular pathway displays a high level of structural and functional specialization, with the membrane-spanning complexes of the tight junctions, adherens junctions, and desmosomes ensuring its integrity. Tight junction proteins, like occludin, tricellulin, and the claudin family isoforms, play prominent roles as barriers to unrestricted paracellular transport. The past decade has witnessed major advances in our understanding of the architecture and function of epithelial tight junctions. While it has been long appreciated that microbes, notably bacterial and viral pathogens, target and disrupt junctional complexes and alter paracellular permeability, the precise mechanisms remain to be defined. Notably, renewed efforts will be required to interpret the available data on pathogen-mediated barrier disruption in the context of the most recent findings on tight junction structure and function. While much of the focus has been on pathogen-induced dysregulation of junctional complexes, commensal microbiota and their products may influence paracellular permeability and contribute to the normal physiology of the gut. Finally, microbes and their products have become important tools in exploring host systems, including the junctional properties of epithelial cells. © 2018 American Physiological Society. Compr Physiol 8:823-842, 2018.

Metallochaperone UreG serves as a new target for design of urease inhibitor: A novel strategy for development of antimicrobials

Urease as a potential target of antimicrobial drugs has received considerable attention given its versatile roles in microbial infection. Development of effective urease inhibitors, however, is a significant challenge due to the deeply buried active site and highly specific substrate of a bacterial urease. Conventionally, urease inhibitors are designed by either targeting the active site or mimicking substrate of urease, which is not efficient. Up to now, only one effective inhibitor—acetohydroxamic acid (AHA)—is clinically available, but it has adverse side effects. Herein, we demonstrate that a clinically used drug, colloidal bismuth subcitrate, utilizes an unusual way to inhibit urease activity, i.e., disruption of urease maturation process via functional perturbation of a metallochaperone, UreG. Similar phenomena were also observed in various pathogenic bacteria, suggesting that UreG may serve as a general target for design of new types of urease inhibitors. Using Helicobacter pylori UreG as a showcase, by virtual screening combined with experimental validation, we show that two compounds targeting UreG also efficiently inhibited urease activity with inhibitory concentration (IC)₅₀ values of micromolar level, resulting in attenuated virulence of the pathogen. We further demonstrate the efficacy of the compounds in a mammalian cell infection model. This study opens up a new opportunity for the design of more effective urease inhibitors and clearly indicates that metallochaperones involved in the maturation of important microbial metalloenzymes serve as new targets for devising a new type of antimicrobial drugs.

Urease, a metalloenzyme that catalyzes the hydrolysis of urea, plays important roles in the survival and virulence of many microbial pathogens, and has long been considered an important drug target for the development of novel antimicrobials. However, its deeply buried active site and highly specific substrate of bacterial urease make it very challenging to design effective urease inhibitors by conventional approaches. In this study, we reveal that a bismuth-based drug (colloidal bismuth subcitrate) inhibits urease activity in an unusual way. This drug binds the urease accessary protein UreG and inhibits its GTPase activity, thus perturbing nickel insertion into the apo-urease, a process called urease maturation. UreG is therefore proposed as an alternative target for the development of urease inhibitors. Using H. pylori UreG as an example, combined with virtual screening and experimental validation, we further show that several small molecules that bind and functionally disrupt UreG could indeed inhibit urease activity in bacteria and in a cell infection model and possess potent antimicrobial activity. In summary, we discovered metallochaperone UreG as a new target for the design of urease inhibitors. Such a strategy should have a broad application in the development of metalloenzyme inhibitors.

miR-143 inhibits intracellular salmonella growth by targeting ATP6V1A in macrophage cells in pig

Salmonella infects many vertebrate species, and animals such as pigs can be colonized with Salmonella and become established carriers. Analyzing the roles of microRNA in intracellular proliferation is important for understanding the process of Salmonella infection. The objective of this study is to verify the regulation effect of miR-143 on ATP6V1A and its functions in the intracellular growth of Salmonella. A new miR-143 binding site was discovered in the 3' UTR of ATP6V1A using a newly developed prediction tool. The binding site was confirmed by binding site deletion assay. Real-time PCR results indicated that ATP6V1A was predominantly expressed in bone-marrow-derived macrophages, and the expression of miR-143 in different tissues was negatively correlated with ATP6V1A. The Salmonella proliferation assay showed that the expression of miR-143 could inhibit intracellular Salmonella growth in macrophages by target ATP6V1A. The results strongly suggest that miR-143 plays important regulatory roles in the development of Salmonella infection in animals.

Helicobacter pylori VacA induces autophagic cell death in gastric epithelial cells via the endoplasmic reticulum stress pathway

The Helicobacter pylori vacuolating cytotoxin (VacA) can promote progressive vacuolation and gastric injury and may be associated with human gastric cancer. Increasing evidence indicates that autophagy is involved in the cell death induced by VacA, but the specific mechanisms need to be further elucidated. We show here that VacA could induce autophagy and increase cell death in human gastric cancer cell lines. Further investigations revealed that inhibition of autophagy could decrease the VacA-induced cell death in AGS cells. Furthermore, numerous dilated endoplasmic reticula (ER) were observed, and the phosphorylation of a subunit of eukaryotic translation initiation factor 2 subunit 1 also increased in the VacA-treated AGS cells, while repression of ER stress could reduce autophagy and cell death through knockdown of activating transcription factor 4 and DNA-damage-inducible transcript 3. In addition, the expression of pseudokinase tribbles homolog 3 (TRIB3) upon ER stress was triggered by VacA, and knockdown of TRIB3 could also decrease VacA-induced cell death. Finally, inhibition of autophagy could decrease VacA^s1m1-induced cell death and apoptosis, and apoptosis inhibitor Z-VAD had no significant effect on autophagy induced by VacA^s1m1. Thus, these results suggested that VacA causes autophagic cell death via ER stress in gastric epithelial cells.

Helicobacter pylori antigenic Lpp20 is a structural homologue of Tipα and promotes epithelial-mesenchymal transition

BACKGROUND

Helicobacter pylori is a bacterium that affects about 50% of the world population and, despite being often asymptomatic, it is responsible of several gastric diseases, from gastritis to gastric cancer. The protein Lpp20 (HP1456) plays an important role in bacterium survival and host colonization, but the possibility that it might be involved in the etiology of H. pylori-related disorders is an unexplored issue. Lpp20 is a lipoprotein bound to the external membrane of the bacterium, but it is also secreted inside vesicles along with other two proteins of the same operon, i.e. HP1454 and HP1457.

RESULTS

In this study we determined the crystal structure of Lpp20 and we found that it has a fold similar to a carcinogenic factor released by H. pylori, namely Tipα. We demonstrate that Lpp20 promotes cell migration and E-cadherin down-regulation in gastric cancer cells, two events recalling the epithelial-mesenchymal transition (EMT) process. Differently from Tipα, Lpp20 also stimulates cell proliferation.

CONCLUSIONS

This identifies Lpp20 as a new pathogenic factor produced by H. pylori that promotes EMT and thereby the progression of cancer to the metastatic state.

A Helicobacter pylori Homolog of Eukaryotic Flotillin Is Involved in Cholesterol Accumulation, Epithelial Cell Responses and Host Colonization

The human pathogen Helicobacter pylori acquires cholesterol from membrane raft domains in eukaryotic cells, commonly known as "lipid rafts." Incorporation of this cholesterol into the H. pylori cell membrane allows the bacterium to avoid clearance by the host immune system and to resist the effects of antibiotics and antimicrobial peptides. The presence of cholesterol in H. pylori bacteria suggested that this pathogen may have cholesterol-enriched domains within its membrane. Consistent with this suggestion, we identified a hypothetical H. pylori protein (HP0248) with homology to the flotillin proteins normally found in the cholesterol-enriched domains of eukaryotic cells. As shown for eukaryotic flotillin proteins, HP0248 was detected in detergent-resistant membrane fractions of H. pylori. Importantly, H. pylori HP0248 mutants contained lower levels of cholesterol than wild-type bacteria (P < 0.01). HP0248 mutant bacteria also exhibited defects in type IV secretion functions, as indicated by reduced IL-8 responses and CagA translocation in epithelial cells (P < 0.05), and were less able to establish a chronic infection in mice than wild-type bacteria (P < 0.05). Thus, we have identified an H. pylori flotillin protein and shown its importance for bacterial virulence. Taken together, the data demonstrate important roles for H. pylori flotillin in host-pathogen interactions. We propose that H. pylori flotillin may be required for the organization of virulence proteins into membrane raft-like structures in this pathogen.

A novel isolation protocol and probe-based RT-PCR for diagnosis of gastric infections with the zoonotic pathogen Helicobacter suis

BACKGROUND

Helicobacter suis is a very fastidious microorganism associated with gastritis, gastric ulcers, and mucosa-associated lymphoid tissue lymphoma in humans. In vitro isolation of this agent from human patients has so far been unsuccessful.

MATERIALS AND METHODS

A probe-based real-time PCR (RT-PCR) for the rapid detection of H. suis in gastric biopsies was developed. Secondly, a mouse-passage-based protocol was optimized for isolation of low numbers of viable H. suis bacteria. Mice were inoculated with different numbers of viable H. suis (10² -10⁸ ) and kept for 4 weeks to allow multiplication of this pathogen.

RESULTS

The probe-based real-time PCR (RT-PCR) exhibited a high degree of diagnostic specificity and analytical sensitivity, high linear correlations (r² between 0.995 and 0.999), and high amplification efficiencies (>90%) for H. suis. No cross-reactivity was detected with human, porcine, non-human primate, and murine DNA nor with DNA from other bacteria including Helicobacter spp. and Campylobacter spp. H. suis was successfully re-isolated from the stomach of mice inoculated with at least 10⁴ viable H. suis, using a biphasic medium (pH 5), consisting of Brucella agar with Brucella broth on top, both supplemented with vitox supplement, Campylobacter-selective supplement, amphotericin (5 μg/mL), HCl (0.05%), fetal bovine serum (20%), and linezolid (5 μg/mL). Linezolid was necessary to inhibit proliferation of contaminants, including lactobacilli.

CONCLUSION

The methods described above can be implemented for detection or isolation of H. suis from human gastric biopsies.

Integrative approach for the analysis of the proteome-wide response to bismuth drugs in Helicobacter pylori

An integrative metalloproteomic approach to unveil the role of antimicrobial metals in general using bismuth as an example.

Bismuth drugs, despite being clinically used for decades, surprisingly remain in use and effective for the treatment of Helicobacter pylori infection, even for resistant strains when co-administrated with antibiotics. However, the molecular mechanisms underlying the clinically sustained susceptibility of H. pylori to bismuth drugs remain elusive. Herein, we report that integration of in-house metalloproteomics and quantitative proteomics allows comprehensive uncovering of the bismuth-associated proteomes, including 63 bismuth-binding and 119 bismuth-regulated proteins from Helicobacter pylori, with over 60% being annotated with catalytic functions. Through bioinformatics analysis in combination with bioassays, we demonstrated that bismuth drugs disrupted multiple essential pathways in the pathogen, including ROS defence and pH buffering, by binding and functional perturbation of a number of key enzymes. Moreover, we discovered that HpDnaK may serve as a new target of bismuth drugs to inhibit bacterium-host cell adhesion. The integrative approach we report, herein, provides a novel strategy to unveil the molecular mechanisms of antimicrobial metals against pathogens in general. This study sheds light on the design of new types of antimicrobial agents with multiple targets to tackle the current crisis of antimicrobial resistance.

The Helicobacter pylori Autotransporter ImaA Tempers the Bacterium's Interaction with α5β1 Integrin

The human pathogen Helicobacter pylori uses the host receptor α₅β₁ integrin to trigger inflammation in host cells via its cag pathogenicity island (cag PAI) type IV secretion system (T4SS). Here, we report that the H. pylori ImaA protein (HP0289) decreases the action of the cag PAI T4SS via tempering the bacterium's interaction with α₅β₁ integrin. Previously, imaA-null mutants were found to induce an elevated inflammatory response that was dependent on the cag PAI T4SS; here we extend those findings to show that the elevated response is independent of the CagA effector protein. To understand how ImaA could be affecting cag PAI T4SS activity at the host cell interface, we utilized the Phyre structural threading program and found that ImaA has a region with remote homology to bacterial integrin-binding proteins. This region was required for ImaA function. Unexpectedly, we observed that imaA mutants bound higher levels of α₅β₁ integrin than wild-type H. pylori, an outcome that required the predicted integrin-binding homology region of ImaA. Lastly, we report that ImaA directly affected the amount of host cell β1 integrin but not other cellular integrins. Our results thus suggest a model in which H. pylori employs ImaA to regulate interactions between integrin and the T4SS and thus alter the host inflammatory strength.

Dynamics of a microorganism in a sheared viscoelastic liquid

In this paper, we investigate the dynamics of a model spherical microorganism, called squirmer, suspended in a viscoelastic fluid undergoing unconfined shear flow. The effect of the interplay of shear flow, fluid viscoelasticity, and self-propulsion on the orientational dynamics is addressed. In the limit of weak viscoelasticity, quantified by the Deborah number, an analytical expression for the squirmer angular velocity is derived by means of the generalized reciprocity theorem. Direct finite element simulations are carried out to study the squirmer dynamics at larger Deborah numbers. Our results show that the orientational dynamics of active microorganisms in a sheared viscoelastic fluid greatly differs from that observed in Newtonian suspensions. Fluid viscoelasticity leads to a drift of the particle orientation vector towards the vorticity axis or the flow-gradient plane depending on the Deborah number, the relative weight between the self-propulsion velocity and the flow characteristic velocity, and the type of swimming. Generally, pullers and pushers show an opposite equilibrium orientation. The results reported in the present paper could be helpful in designing devices where separation of microorganisms, based on their self-propulsion mechanism, is obtained.

The Upregulation of TRAF1 Induced by Helicobacter pylori Plays an Antiapoptotic Effect on the Infected Cells

BACKGROUND

Tumor necrosis factor receptor-associated factor 1 (TRAF1) is a member of the TRAF family and is dysregulated in diseases, such as atheroma, lymphoma, and solid tumors, but the role of TRAF1 in gastric cancer remains unknown. This study was aimed to investigate the role of TRAF1 in Helicobacter pylori (H. pylori)-related cell apoptosis and gastric carcinogenesis.

MATERIALS AND METHODS

The mRNA and protein expression levels of TRAF1 were measured in a panel of gastric cancer cell lines and in H. pylori -infected mice by quantitative real-time PCR (qPCR) and Western blotting. The transcription factor that mainly affects transcription of TRAF1 during H. pylori infection was identified. The roles of H. pylori virulence factors that regulate TRAF1 expression were analyzed using isogenic cagA-, vacA-, and cagE-null mutants. The effects of TRAF1 on gastric cell viability and apoptosis during H. pylori infection were detected using the standard MTS (cell viability) assay and flow cytometry, respectively.

RESULTS

H. pylori infection induced TRAF1 overexpression in both gastric epithelial cells and mice. The expression of TRAF1 in response to H. pylori infection was majorly regulated by the activation of NF-κB and was strongly related to H. pylori virulence factor CagA. The upregulation of TRAF1 inhibited cell apoptosis and increased the viability of infected cells.

CONCLUSIONS

H. pylori infection induces the overexpression of TRAF1 in gastric epithelial cells. The upregulation of TRAF1 plays an antiapoptotic role in H. pylori -infected gastric cells and may contribute to the gastric carcinogenesis.

The Helicobacter heilmannii hofE and hofF Genes are Essential for Colonization of the Gastric Mucosa and Play a Role in IL-1β-Induced Gastric MUC13 Expression

BACKGROUND

Helicobacter heilmannii is a zoonotic bacterium associated with gastric disease in humans. We recently showed that H. heilmannii binds to human gastric mucins and epithelial cells and highlighted a potential role for the murine Muc13 mucin in gastric Helicobacter colonization. The aims of this study were to investigate the role of the H. heilmannii hof gene locus encoding HofH/F/E/G/C/D in adhesion to the gastric mucosa and induction of increased gastric Muc13 expression.

METHODS

Bacterial hof gene and host gene expression experiments, Helicobacter binding assays and experimental infection studies in mice were performed. H. pylori and its ΔhofF mutant were included for comparison.

RESULTS

Helicobacter heilmannii strains lacking HofE or HofF showed a clear decrease in binding to gastric mucins and epithelial cells as well as a lower gastric colonization level in the stomach of Balb/c mice at 4 and 9 weeks post-infection compared to the H. heilmannii wildtype strain. Interestingly, H. heilmannii ΔhofE and ΔhofF and H. pylori ΔhofF did not induce an increased expression of MUC13 in human gastric epithelial cells and of Muc13 in the stomach of mice. Finally, we demonstrated that IL-1β is induced in the stomach as a response to Helicobacter colonization which on its turn is involved in the expression of MUC13/Muc13 in the gastric epithelium.

CONCLUSION

These novel results in Helicobacter research identified H. heilmannii HofE and HofF as adhesins and suggest an important role of H. heilmannii HofE and HofF and H. pylori HofF in IL-1β-induced gastric MUC13/Muc13 expression.

Diversification of the vacAs1m1 and vacAs2m2 Strains of Helicobacter pylori in Meriones unguiculatus

The bacterium Helicobacter pylori exhibits great genetic diversity, and the pathogenic roles of its virulence factors have been widely studied. However, the evolutionary dynamics of H. pylori strains during stomach colonization are not well-characterized. Here, we analyzed the microevolutionary dynamics of the toxigenic strain vacAs1m1, the non-toxigenic strain vacAs2m2, and a combination of both strains in an animal model over time. Meriones unguiculatus were inoculated with the following bacteria: group 1-toxigenic strain vacAs1m1/cagA+/cagE+/babA2+; ST181, group 2-non-toxigenic strain vacAs2m2/cagA+/cagE+/babA2+; ST2901, and group 3-both strains. The gerbils were euthanized at different time points (3, 6, 12, and 18 months). In group 1, genetic alterations were observed at 6 and 12 months. With the combination of both strains, group 3 also exhibited genetic alterations at 3 and 18 months; moreover, a chimera, vacA m1-m2, was detected. Additionally, four new sequence types (STs) were reported in the PubMLST database for H. pylori. Synonymous and non-synonymous mutations were analyzed and associated with alterations in amino acids. Microevolutionary analysis of the STs (PHYLOViZ) identified in each group revealed many mutational changes in the toxigenic (vacAs1m1) and non-toxigenic (vacAs2m2) strains. Phylogenetic assessments (eBURST) did not reveal clonal complexes. Our findings indicate that the toxigenic strain, vacAs1m1, and a combination of toxigenic and non-toxigenic strains acquired genetic material by recombination. The allelic combination, vacAs2m1, displayed the best adaptation in the animal model over time, and a chimera, m1-m2, was also identified, which confirmed previous reports.

Helical and rod-shaped bacteria swim in helical trajectories with little additional propulsion from helical shape

It has frequently been hypothesized that the helical body shapes of flagellated bacteria may yield some advantage in swimming ability. In particular, the helical-shaped pathogen Helicobacter pylori is often claimed to swim like a corkscrew through its harsh gastric habitat, but there has been no direct confirmation or quantification of such claims. Using fast time-resolution and high-magnification two-dimensional (2D) phase-contrast microscopy to simultaneously image and track individual bacteria in bacterial broth as well as mucin solutions, we show that both helical and rod-shaped H. pylori rotated as they swam, producing a helical trajectory. Cell shape analysis enabled us to determine shape as well as the rotational and translational speed for both forward and reverse motions, thereby inferring flagellar kinematics. Using the method of regularized Stokeslets, we directly compare observed speeds and trajectories to numerical calculations for both helical and rod-shaped bacteria in mucin and broth to validate the numerical model. Although experimental observations are limited to select cases, the model allows quantification of the effects of body helicity, length, and diameter. We find that due to relatively slow body rotation rates, the helical shape makes at most a 15% contribution to propulsive thrust. The effect of body shape on swimming speeds is instead dominated by variations in translational drag required to move the cell body. Because helical cells are one of the strongest candidates for propulsion arising from the cell body, our results imply that quite generally, swimming speeds of flagellated bacteria can only be increased a little by body propulsion.

MST1-dependent vesicle trafficking regulates neutrophil transmigration through the vascular basement membrane

Neutrophils need to penetrate the perivascular basement membrane for successful extravasation into inflamed tissue, but this process is incompletely understood. Recent findings have associated mammalian sterile 20-like kinase 1 (MST1) loss of function with a human primary immunodeficiency disorder, suggesting that MST1 may be involved in immune cell migration. Here, we have shown that MST1 is a critical regulator of neutrophil extravasation during inflammation. Mst1-deficient (Mst1-/-) neutrophils were unable to migrate into inflamed murine cremaster muscle venules, instead persisting between the endothelium and the basement membrane. Mst1-/- neutrophils also failed to extravasate from gastric submucosal vessels in a murine model of Helicobacter pylori infection. Mechanistically, we observed defective translocation of VLA-3, VLA-6, and neutrophil elastase from intracellular vesicles to the surface of Mst1-/- neutrophils, indicating that MST1 is required for this crucial step in neutrophil transmigration. Furthermore, we found that MST1 associates with the Rab27 effector protein synaptotagmin-like protein 1 (JFC1, encoded by Sytl1 in mice), but not Munc13-4, thereby regulating the trafficking of Rab27-positive vesicles to the cellular membrane. Together, these findings highlight a role for MST1 in vesicle trafficking and extravasation in neutrophils, providing an additional mechanistic explanation for the severe immune defect observed in patients with MST1 deficiency.

The Forgotten Virulence Factor: The 'non-conventional' Hemolysin TlyA And Its Role in Helicobacter pylori Infection

Helicobacter pylori is a human-specific Gram-negative pathogenic bacterium which colonizes the gastric mucosal layer in the stomach causing diseases such as peptic ulcer, adenocarcinoma, and gastric lymphoma. It is estimated that approximately half of the world's population is infected with H. pylori making it the most intensively characterized microbial pathogen up to now. Hemolysis has been suggested to significantly contribute to colonization of the stomach and disease progression by H. pylori. In a number of earlier studies, TlyA was characterized as a putative pore-forming cytolysin. Although a few observations in the literature suggest a role for TlyA as significant virulence factor of H. pylori, the molecular and structural characterization of this protein is much curtailed at present. Given the intensive characterization of numerous H. pylori virulence factors over the past decade, surprisingly little information exists for the TlyA toxin and its significance for pathogenesis. This review provides a brief overview on microbial hemolysis and its role for pathogenesis and discusses recent research efforts aimed at an improved understanding of the role of the 'non-conventional' hemolysin and its associated RNA methyltransferase TlyA from H. pylori.

Dietary Patterns are Associated with Helicobacter Pylori Infection in Chinese Adults: A Cross-Sectional Study

Previous studies indicated that food consumption was associated with Helicobacter pylori infection, but no study has yet investigated the association between Helicobacter pylori infection and dietary patterns. The aim of this study was to evaluate the associations between Helicobacter pylori infection and dietary patterns in Tianjin, China. The final cross-sectional study population comprised 10407 participants. Dietary consumption of participants was assessed via food frequency questionnaire. Factor analysis was used to identify dietary patterns, and Helicobacter pylori infection status was diagnosis by H. pylori urease Immunogold Testing kit. Participants in the highest quartile of the high-carbohydrate/sweet pattern showed a multivariable-adjusted OR (95% CI) of 1.65 (1.27–2.17) for the prevalence of H. pylori infection compared with those in the lowest quartile. The multiple adjusted OR for scores of the extreme quartile of high-protein/cholesterol pattern was 0.75 (95% CI, 0.57–0.98). This study demonstrated that a diet rich in carbohydrates and sweets was positively associated with the prevalence of H. pylori infection; interestingly, a diet characterized by high intake of animal offal, animal blood, fish, seafood, and poultry was associated with a reduction of prevalence of H. pylori infection.

Solution-phase microwave assisted parallel synthesis, biological evaluation and in silico docking studies of N,N'-disubstituted thioureas derived from 3-chlorobenzoic acid

A facile and robust microwave-assisted solution phase parallel synthesis protocol was exercised for the development of a 38-member library of N,N'-disubstituted thiourea analogues (1-38) by using an identical set of conditions. The reaction time for synthesis of N,N'-disubstituted thiourea analogues was drastically reduced from a reported duration of 8-12h for conventional methods to only 1.5-2.0min. All the derivatives (1-38) were characterized by physico-analytical techniques such as elemental analysis in combination with FT-IR, (1)H, (13)C NMR and by single crystal XRD analysis have also been performed. These compounds were screened for their in vitro urease inhibition activities. Majority of compounds exhibited potent urease inhibition activities, however, the most significant activity was found for 16, with an IC50 value of 1.23±0.1μM. Furthermore, the synthesized compounds were screened for their cytotoxic potential against lungs cancer cell lines. Cell culture studies demonstrated significant toxicity of the compounds on the cell lines, and the levels of toxicity were altered in the presence of various side groups. The molecular docking studies of the most potent inhibitors were performed to identify the probable binding modes in the active site of the urease enzymes. These compounds have a great potential and significance for further investigations.

An Overview of Helicobacter pylori VacA Toxin Biology

The VacA toxin secreted by Helicobacter pylori enhances the ability of the bacteria to colonize the stomach and contributes to the pathogenesis of gastric adenocarcinoma and peptic ulcer disease. The amino acid sequence and structure of VacA are unrelated to corresponding features of other known bacterial toxins. VacA is classified as a pore-forming toxin, and many of its effects on host cells are attributed to formation of channels in intracellular sites. The most extensively studied VacA activity is its capacity to stimulate vacuole formation, but the toxin has many additional effects on host cells. Multiple cell types are susceptible to VacA, including gastric epithelial cells, parietal cells, T cells, and other types of immune cells. This review focuses on the wide range of VacA actions that are detectable in vitro, as well as actions of VacA in vivo that are relevant for H. pylori colonization of the stomach and development of gastric disease.

New Insights into VacA Intoxication Mediated through Its Cell Surface Receptors

Helicobacter pylori (H. pylori), a major cause of gastroduodenal diseases, produces VacA, a vacuolating cytotoxin associated with gastric inflammation and ulceration. The C-terminal domain of VacA plays a crucial role in receptor recognition on target cells. We have previously identified three proteins (i.e., RPTPα, RPTPβ, and LRP1) that serve as VacA receptors. These receptors contribute to the internalization of VacA into epithelial cells, activate signal transduction pathways, and contribute to cell death and gastric ulceration. In addition, other factors (e.g., CD18, sphingomyelin) have also been identified as cell-surface, VacA-binding proteins. Since we believe that, following interactions with its host cell receptors, VacA participates in events leading to disease, a better understanding of the cellular function of VacA receptors may provide valuable information regarding the mechanisms underlying the pleiotropic actions of VacA and the pathogenesis of H. pylori-mediated disease. In this review, we focus on VacA receptors and their role in events leading to cell damage.

Helicobacter pylori Couples Motility and Diffusion to Actively Create a Heterogeneous Complex Medium in Gastric Mucus

Helicobacter pylori swims through mucus gel by generating ammonia that locally neutralizes the acidic gastric environment, turning nearby gel into a fluid pocket. The size of the fluid zone is important for determining the physics of the motility: in a large zone swimming occurs as in a fluid through hydrodynamic principles, while in a very small zone the motility could be strongly influenced by nonhydrodynamic cell-mucus interactions including chemistry and adhesion. Here, we calculate the size of the fluid pocket. We model how swimming depends on the de-gelation range using a Taylor sheet swimming through a layer of Newtonian fluid bounded by a Brinkman fluid. Then, we model how the de-gelation range depends on the swimming speed by considering the advection-diffusion of ammonia exuded from a translating sphere. Self-consistency between both models determines the values of the swimming speed and the de-gelation range. We find that H. pylori swims through mucus as if unconfined, in a large pocket of Newtonian fluid.